Semi-active architectures for batteries having two different chemistries

Abstract

A 12 volt automotive battery system includes a first battery coupled to an electrical system, in which the first battery includes a first battery chemistry. The first battery is charged with a relatively constant first voltage, in which an alternator outputs the relatively constant first voltage. The 12 volt automotive battery system further includes a second battery coupled in parallel with the first battery and selectively coupled to the electrical system via a DC/DC converter, in which the second battery includes a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry. The DC/DC converter boosts the first voltage to a second voltage to charge the second battery during regenerative braking, in which the second voltage is higher than a maximum charging voltage of the first battery.

The invention claimed is: 
     
       1. A 12 volt automotive battery system, comprising:
 a first battery configured to be coupled to an electrical system and to be charged with a relatively constant first voltage, wherein an alternator outputs the first voltage, and the first battery comprises a first battery chemistry; 
 a second battery comprising a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; 
 a DC/DC converter coupled in series with the second battery, wherein the DC/DC converter and the second battery are coupled in parallel with the first battery, and the DC/DC converter is configured to:
 selectively couple the second battery to the electrical system; and 
 boost the first voltage to a second voltage to charge the second battery during regenerative braking, wherein the second voltage is higher than a maximum charging voltage of the first battery; and 
 
 a housing that houses the first battery, the second battery, and the DC/DC converter, wherein the housing comprises a positive terminal and a ground terminal coupled to the first battery and selectively coupled to the second battery via the DC/DC converter, wherein the positive terminal and the ground terminal are configured to couple to the electrical system. 
 
     
     
       2. The battery system of  claim 1 , comprising a battery control unit configured to maintain the first battery generally at a full state of charge before regenerative braking to enable the first battery to steer power generated during regenerative braking to the second battery using internal resistance of the first battery. 
     
     
       3. The battery system of  claim 1 , wherein the maximum charging voltage of the first battery is lower than maximum charging voltage of the second battery. 
     
     
       4. The battery system of  claim 1 , wherein the second voltage is between 14.8 to 16.8 volts when the first battery chemistry is lead-acid and the second battery chemistry is lithium nickel manganese cobalt oxide. 
     
     
       5. The battery system of  claim 1 , comprising a switch coupled in series with the first battery, wherein the switch is configured to be selectively couple the first battery to the electrical system. 
     
     
       6. A method for operating a 12 volt automotive battery system, comprising:
 charging, using an alternator, a first battery by outputting a relatively constant first voltage, wherein the first battery comprises a first battery chemistry; and 
 boosting, using a DC/DC converter, the first voltage to a second voltage during regenerative braking to charge a second battery using the second voltage, wherein:
 the second voltage is higher than a maximum charging voltage of the first battery; 
 the second battery comprises a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; 
 the DC/DC converter is coupled in series with the second battery; 
 the DC/DC converter and the second battery are coupled in parallel with the first battery during regenerative braking; and 
 charging the first battery comprises maintaining the first battery generally at a full state of charge before regenerative braking to enable the first battery to steer power generated during regenerative braking to the second battery using internal resistance of the first battery. 
 
 
     
     
       7. The method of  claim 6 , wherein the second voltage is between 14.8 to 16.8 volts when the first battery chemistry is lead-acid and the second battery chemistry is lithium nickel manganese cobalt oxide. 
     
     
       8. The method of  claim 6 , wherein boosting the first voltage to the second voltage with the DC/DC converter comprises:
 disconnecting, using a DC/DC converter switch, a bypass path in the DC/DC converter; and 
 connecting, using the DC/DC converter switch, a boost path in the DC/DC converter. 
 
     
     
       9. The method of  claim 6 , wherein the maximum charging voltage of first battery is lower than maximum charging voltage of the second battery. 
     
     
       10. A 12 volt automotive battery system, comprising:
 a first battery configured to be charged with a relatively constant first voltage, wherein the relatively constant first voltage is output by an alternator during regenerative braking, and the first battery comprises a first battery chemistry; and 
 a DC/DC converter configured to be coupled in series with a second battery comprising a second battery chemistry, wherein the DC/DC converter comprises:
 a converter path configured to:
 connect the DC/DC converter and the second battery in parallel with the first battery; and 
 charge the second battery during regenerative braking by boosting the first voltage to a second voltage; 
 
 a bypass path configured to:
 connect the second battery in parallel with the first battery; and 
 enable the second battery to supply power when voltage of the second battery is higher than the first voltage and the second battery has a positive state of charge; and 
 
 a DC/DC converter switch configured to selectively switch between the converter path and the bypass path. 
 
 
     
     
       11. The battery system of  claim 10 , wherein the second voltage is higher than a maximum charging voltage of the first battery. 
     
     
       12. The battery system of  claim 11 , wherein the first battery is configured to produce oxygen gas or hydrogen gas when charged at a voltage above the maximum charging voltage. 
     
     
       13. The battery system of  claim 10 , comprising a housing that houses the first battery, the second battery, and the DC/DC converter, wherein the housing comprises a positive terminal and a ground terminal coupled to the first battery and selectively coupled to the second battery via the DC/DC converter, wherein the positive terminal and the ground terminal are configured to couple to an electrical system. 
     
     
       14. The battery system of  claim 10 , wherein the first battery and the second battery are non-voltage matched such that a first voltage range of the second battery is higher than a second voltage range of the first battery and do not overlap, wherein:
 the second voltage range comprises open circuit voltage of the first battery from 0-100% state of charge; and 
 the first voltage range comprises open circuit voltage of the second battery from 0-100% state of charge. 
 
     
     
       15. The battery system of  claim 10 , wherein the first battery chemistry is lead-acid and the second battery chemistry is lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, or lithium nickel manganese cobalt oxide-lithium nickel cobalt aluminum oxide. 
     
     
       16. The battery system of  claim 10 , wherein the first battery and the second battery are partial voltage matched such that a first voltage range of the first battery and a second voltage range of the second battery partially overlap, wherein:
 the first voltage range comprises open circuit voltage of the first battery from 0-100% state of charge; 
 the second voltage range comprises open circuit voltage of the second battery from 0-100% state of charge; and 
 a portion of the second voltage range that overlaps with the first voltage range corresponds to open circuit voltage of the second battery from 1-74% state of charge. 
 
     
     
       17. The battery system of  claim 10 , wherein the first battery chemistry is lead-acid and the second battery chemistry is lithium-titanate/lithium nickel manganese cobalt oxide, nickel-metal hydride, or lithium iron phosphate. 
     
     
       18. A 12 volt automotive battery system, comprising:
 a first battery configured to be charged with a relatively constant first voltage, wherein an alternator outputs the relatively constant first voltage, and the first battery comprises a first battery chemistry; and 
 a DC/DC converter configured to be coupled in series with a second battery comprising a second battery chemistry, wherein the DC/DC converter comprises:
 a converter path configured to:
 connect the DC/DC converter and the second battery in parallel with the first battery; and 
 enable the second battery to supply power by boosting voltage of the second battery to the first voltage when the second battery has a positive state of charge; 
 
 a bypass path configured to
 connect the second battery in parallel with the first battery; and 
 enable the second battery to be charged during regenerative braking when the voltage of the second battery is lower than the first voltage; and 
 
 a DC/DC converter switch configured to selectively switch between the converter path and the bypass path. 
 
 
     
     
       19. The battery system of  claim 18 , wherein the first battery and the second battery are voltage matched such that a first voltage range of the first battery and a second voltage range of the second battery largely overlap, wherein:
 the first voltage range comprises open circuit voltage of the first battery from 0-100% state of charge; 
 the second voltage range comprises open circuit voltage of the second battery from 0-100% state of charge; and 
 a portion of the second voltage range that overlaps with the first voltage range corresponds to open circuit voltage of the second battery from 75-100% state of charge. 
 
     
     
       20. The battery system of  claim 18 , wherein the first battery chemistry is lead-acid and the second battery chemistry is lithium-titanate/lithium manganese oxide or nickel-zinc. 
     
     
       21. A 12 volt automotive battery system, comprising:
 a first battery configured to be coupled to an electrical system and to be charged with a relatively constant first voltage, wherein an alternator outputs the first voltage, and the first battery comprises a first battery chemistry; and 
 a second battery comprising a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; and 
 a DC/DC converter coupled in series with the second battery, wherein the DC/DC converter and the second battery are coupled in parallel with the first battery, and the DC/DC converter is configured to:
 selectively couple the second battery to the electrical system; and 
 boost the first voltage to a second voltage to charge the second battery during regenerative braking, wherein the second voltage is higher than a maximum charging voltage of the first battery, wherein the first battery is configured to produce oxygen gas or hydrogen gas when charged at a voltage above the maximum charging voltage. 
 
 
     
     
       22. A 12 volt automotive battery system, comprising:
 a first battery configured to be coupled to an electrical system and to be charged with a relatively constant first voltage, wherein an alternator outputs the first voltage, and the first battery comprises a first battery chemistry; and 
 a second battery comprising a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; and 
 a DC/DC converter coupled in series with the second battery, wherein the DC/DC converter and the second battery are coupled in parallel with the first battery, and the DC/DC converter comprises:
 a converter path configured to boost the first voltage to a second voltage to charge the second battery during regenerative braking, wherein the second voltage is higher than a maximum charging voltage of the first battery; 
 a bypass path configured to enable the second battery to supply power when voltage of the second battery is higher than the first voltage; and 
 a DC/DC converter switch configured to selectively switch between the converter path and the bypass path. 
 
 
     
     
       23. A 12 volt automotive battery system, comprising:
 a first battery configured to be coupled to an electrical system and to be charged with a relatively constant first voltage, wherein an alternator outputs the first voltage, and the first battery comprises a first battery chemistry; and 
 a second battery comprising a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; and 
 a DC/DC converter coupled in series with the second battery, wherein the DC/DC converter and the second battery are coupled in parallel with the first battery, and the DC/DC converter is configured to:
 selectively couple the second battery to the electrical system; and 
 boost the first voltage to a second voltage to charge the second battery during regenerative braking, wherein the second voltage is higher than a maximum charging voltage of the first battery; 
 
 wherein the first battery and the second battery are non-voltage matched such that a first voltage range of the second battery is higher than a second voltage range of the first battery and do not overlap, wherein:
 the first voltage range comprises open circuit voltage of the first battery from 0-100% state of charge; and 
 the second voltage range comprises open circuit voltage of the second battery from 0-100% state of charge. 
 
 
     
     
       24. A 12 volt automotive battery system, comprising:
 a first battery configured to be coupled to an electrical system and to be charged with a relatively constant first voltage, wherein an alternator outputs the first voltage, and the first battery comprises a first battery chemistry; and 
 a second battery comprising a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; and 
 a DC/DC converter coupled in series with the second battery, wherein the DC/DC converter and the second battery are coupled in parallel with the first battery, and the DC/DC converter is configured to:
 selectively couple the second battery to the electrical system; and 
 boost the first voltage to a second voltage to charge the second battery during regenerative braking, wherein the second voltage is higher than a maximum charging voltage of the first battery; 
 
 wherein the first battery chemistry is lead-acid and the second battery chemistry is lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, or lithium nickel manganese cobalt oxide-lithium nickel cobalt aluminum oxide. 
 
     
     
       25. A 12 volt automotive battery system, comprising:
 a first battery configured to be coupled to an electrical system and to be charged with a relatively constant first voltage, wherein an alternator outputs the first voltage, and the first battery comprises a first battery chemistry; and 
 a second battery comprising a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; and 
 a DC/DC converter coupled in series with the second battery, wherein the DC/DC converter and the second battery are coupled in parallel with the first battery, and the DC/DC converter is configured to:
 selectively couple the second battery to the electrical system; and 
 boost the first voltage to a second voltage to charge the second battery during regenerative braking, wherein the second voltage is higher than a maximum charging voltage of the first battery; 
 
 wherein the first battery and the second battery are partial voltage matched such that a first voltage range of the first battery and a second voltage range of the second battery partially overlap, wherein:
 the first voltage range comprises open circuit voltage of the first battery from 0-100% state of charge; 
 the second voltage range comprises open circuit voltage of the second battery from 0-100% state of charge; and 
 a portion of the second voltage range that overlaps with the first range corresponds to open circuit voltage of the second battery from 1-74% state of charge. 
 
 
     
     
       26. A 12 volt automotive battery system, comprising:
 a first battery configured to be coupled to an electrical system and to be charged with a relatively constant first voltage, wherein an alternator outputs the first voltage, and the first battery comprises a first battery chemistry; and 
 a second battery comprising a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; and 
 a DC/DC converter coupled in series with the second battery, wherein the DC/DC converter and the second battery are coupled in parallel with the first battery, and the DC/DC converter is configured to:
 selectively couple the second battery to the electrical system; and 
 boost the first voltage to a second voltage to charge the second battery during regenerative braking, wherein the second voltage is higher than a maximum charging voltage of the first battery; 
 
 wherein the first battery chemistry is lead-acid and the second battery chemistry is lithium-titanate/lithium nickel manganese cobalt oxide, nickel-metal hydride, or lithium iron phosphate. 
 
     
     
       27. A method for operating a 12 volt automotive battery system, comprising:
 charging, using an alternator, a first battery by outputting a relatively constant first voltage, wherein the first battery comprises a first battery chemistry; and 
 boosting, using a DC/DC converter, the first voltage to a second voltage during regenerative braking to charge a second battery using the second voltage, wherein:
 the second voltage is higher than a maximum charging voltage of the first battery; 
 the second battery comprises a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; 
 the DC/DC converter is coupled in series with the second battery; 
 the DC/DC converter and the second battery are coupled in parallel with the first battery during regenerative braking; and 
 the first battery and the second battery are non-voltage matched such that a first voltage range of the second battery is higher than a second voltage range of the first battery and do not overlap, wherein:
 the first voltage range comprises open circuit voltage of the first battery from 0-100% state of charge; and 
 the second voltage range comprises open circuit voltage of the second battery from 0-100% state of charge. 
 
 
 
     
     
       28. A method for operating a 12 volt automotive battery system, comprising:
 charging, using an alternator, a first battery by outputting a relatively constant first voltage, wherein the first battery comprises a first battery chemistry; and 
 boosting, using a DC/DC converter, the first voltage to a second voltage during regenerative braking to charge a second battery using the second voltage, wherein:
 the second voltage is higher than a maximum charging voltage of the first battery; 
 the second battery comprises a second battery chemistry that has a higher coulombic efficiency than the first battery chemistry; 
 the DC/DC converter is coupled in series with the second battery; 
 the DC/DC converter and the second battery are coupled in parallel with the first battery during regenerative braking; and 
 the first battery and the second battery are partial voltage matched such that a first voltage range of the first battery and a second voltage range of the second battery partially overlap, wherein:
 the first voltage range comprises open circuit voltage of the first battery from 0-100% state of charge; 
 the second voltage range comprises open circuit voltage of the second battery from 0-100% state of charge; and 
 a portion of the second voltage range that overlaps with the first range corresponds to open circuit voltage of the second battery from 1-74% state of charge.